Showing papers in "Dental Materials Journal in 2008"
TL;DR: Findings of this study revealed that bonding between veneering ceramics and zirconia might be based on chemical bonds and that sandblasting was not a necessary surface pretreatment to enhance bond strength and that regeneration firing was not recommended.
Abstract: Aim of the investigation was to assess the effect of different surface treatments on the bond strength of veneering ceramics to zirconia. In a shear test, the influences of polishing, sandblasting, and silica-coating of the zirconia surface on bonding were assessed with five different veneering ceramics. In addition the effect of liner application was examined. With one veneering ceramic, the impact of regeneration firing of zirconia was also evaluated. Statistical analysis was performed with one-way ANOVA and post hoc Scheffe's test. Failure in every case occurred in the veneering ceramic adjacent to the interface with a thin layer of ceramic remaining on the zirconia surface, indicating that bond strength was higher than the cohesive strength of the veneering ceramic. Shear strength ranged from 23.5 +/- 3.4 MPa to 33.0 +/- 6.8 MPa without explicit correlation to the respective surface treatment. Regeneration firing significantly decreased the shear strength of both polished and sandblasted surfaces. Findings of this study revealed that bonding between veneering ceramics and zirconia might be based on chemical bonds. On this note, sandblasting was not a necessary surface pretreatment to enhance bond strength and that regeneration firing was not recommended.
229 citations
TL;DR: It was concluded that sandblasting induced tetragonal-to-monoclinic phase transformation and that the volume expansion associated with such a phase transformation gave rise to an increase in compressive stress on the surface of CZA.
Abstract: Two types of tetragonal zirconia polycrystals (TZP), a ceria-stabilized TZP/Al2O3 nanocomposite (CZA) and a conventional yttria-stabilized TZP (Y-TZP), were sandblasted with 70-microm alumina and 125-microm SiC powders, then partially annealed at 500-1200 degrees C for five minutes Monoclinic ZrO2 content was determined by X-ray diffractometry and Raman spectroscopy Biaxial flexure test was conducted on the specimens before and after the treatments Monoclinic ZrO2 content and biaxial flexure strength increased after sandblasting, but decreased after heat treatment However, in both cases, the strength of CZA was higher than that of Y-TZP Raman spectroscopy showed that a compressive stress field was introduced on the sample surface after sandblasting It was concluded that sandblasting induced tetragonal-to-monoclinic phase transformation and that the volume expansion associated with such a phase transformation gave rise to an increase in compressive stress on the surface of CZA With the occurrence of such a strengthening mechanism in the microstructure, it was concluded that CZA was more susceptible to stress-induced transformation than Y-TZP
224 citations
TL;DR: The performance of chairside conditioning methods used for zirconia was on par with the laboratory alternative tested, and no significant differences were found among the four groups.
Abstract: This study evaluated the effect of chairside and laboratory types of surface conditioning methods on the adhesion of dual-cure resin cement with MDP functional monomer to zirconia ceramic after thermocycling. Disk-shaped (diameter: 10 mm, thickness: 2 mm) Y-TZP ceramics (Lava, 3M ESPE) were used (N=40) and finished with wet 1200-grit silicon carbide abrasive paper. Specimens were randomly divided into four experimental groups according to the following surface conditioning methods (n=10 per group): Group 1--Chairside airborne particle abrasion with 50-microm Al2O2 + Alloy Primer (Kuraray); Group 2--Airborne particle abrasion with 50-microm Al2O3 + Cesead II Opaque Primer (Kuraray); Group 3--Airborne particle abrasion with 50-microm A12O3 + Silano-Pen + silane coupling agent (Bredent); Group 4--Laboratory tribochemical silica coating (110-microm Al2O3 + 110-microm SiOx) (Rocatec) + silane coupling agent (ESPE-Sil). Adhesive cement, Panavia F 2.0 (Kuraray), was bonded incrementally to the ceramic surfaces using polyethylene molds (diameter: 3.6 mm, height: 5 mm). All specimens were thermocycled (5 and 55 degrees C, 6,000 cycles) and subjected to shear bond strength test (1 mm/min). Data were statistically analyzed (one-way ANOVA, alpha=0.05), whereby no significant differences were found among the four groups (8.43+/-1.3, 8.98+/-3.6, 12.02+/-6.7, and 8.23+/-3.8 MPa) (p=0.1357). Therefore, the performance of chairside conditioning methods used for zirconia was on par with the laboratory alternative tested.
219 citations
TL;DR: The single-layer system demonstrated acceptable marginal and internal fit within the limitations of this study, and showed significantly larger internal gaps than Procera copings and crowns.
Abstract: This study evaluated the accuracy of marginal and internal fit between the all-ceramic crowns manufactured by a conventional double-layer computer-aided design/computer-aided manufacturing (CAD/CAM) system and a single-layer system. Ten standardized crowns were fabricated from each of these two systems: conventional double-layer CAD/CAM system (Procera) and a single-layer system (Cerec 3D). The copings and completed crowns were seated on the abutments by a special device that facilitated uniform loading, and the marginal discrepancies were measured. Internal gaps were also measured using a low-viscosity silicone material. Marginal discrepancies of Procera copings were significantly smaller than those of Procera crowns and Cerec 3D crowns (p 0.05). On internal gaps, Cerec 3D crowns showed significantly larger internal gaps than Procera copings and crowns (p < 0.05). Within the limitations of this study, the single-layer system demonstrated acceptable marginal and internal fit.
165 citations
TL;DR: It was concluded that acrylic teeth showed a higher degree of color change and that the amount of colorchange for each group increased proportionally with time.
Abstract: The purpose of this in vitro study was to evaluate the color stability of two brands of porcelain teeth and three brands of acrylic denture teeth. Samples were immersed into three staining drinks as test groups and distilled water as a control. Color measurements of teeth were performed by using a spectrophotometer. Before immersion, the initial color value of each tooth was recorded. Color change values were determined after 1 day, 1 week, 2 weeks, and 4 weeks of immersion. Color differences were characterized using the CIE L*a*b* color space. The color stability of all teeth was significantly affected by the immersion period (p<0.0001). Instant coffee was found to be the most chromogenic agent among the solutions tested (p<0.0001). Among the materials tested, porcelain was found to be more resistant to discoloration. It was concluded that acrylic teeth showed a higher degree of color change and that the amount of color change for each group increased proportionally with time.
146 citations
TL;DR: It was expected that uptake of fluoride ions with cariostatic effect from PRG-Ca fillers would endow dentin substrates with the benefit of secondary caries prevention, together with an effective and durable adhesion to dentin.
Abstract: This paper reviews our recent studies on fluoride-releasing adhesives and the related studies in this field based on information from original research papers, reviews, and patent literatures. A revolutionary PRG (pre-reacted glass ionomer) filler technology--where fillers were prepared by the acid-base reaction of a fluoroaluminosilicate glass with polyalkenoic acid in water, was newly developed, and a new category as "Giomer" was introduced into the market. On fluoride release capability, SIMS examination revealed in vitro fluoride ion uptake by dentin substrate from the PRG fillers in dental adhesive. On bonding durability, it was found that the improved durability of resin-dentin bonds might be achieved not only via the strengthened dentin due to fluoride ion uptake from the PRG-Ca fillers, but also due to retention of relatively insoluble 4-AETCa formed around remnant apatite crystallites within the hybrid layer in 4-AET-containing self-etching adhesives. On ultramorphological study of the resin-dentin interface, TEM images of the PRG-Ca fillers revealed that the dehydrated hydrogel was barely distinguishable from normal glass fillers, if not for the concurrent presence of remnant, incompletely reacted glass cores. In conclusion, it was expected that uptake of fluoride ions with cariostatic effect from PRG-Ca fillers would endow dentin substrates with the benefit of secondary caries prevention, together with an effective and durable adhesion to dentin.
138 citations
TL;DR: SEM images of I-A interface suggested no relationship between the geometrical factors and the type of anti-rotation configuration, and the marginal fit and size of microgap at the implant-abutment interface for several external and internal anti- rotation configurations.
Abstract: To date, there is no evidence that internal anti-rotation configurations are better than external ones. As part of a study to clarify the features and advantages of internal anti-rotation configurations, the objective of the present investigation was to compare and evaluate the marginal fit and size of microgap at the implant-abutment interface for several external and internal anti-rotation configurations. To this end, three internal connection and two external hex connection implant-abutment assemblies were examined in this study. The implant-abutment interface (I-A interface) was evaluated using three geometrical factors: vertical and horizontal discrepancies and size of microgap. Marginal fit and microgap size were measured by a scanning laser microscope. The I-A interface was also observed using a scanning electron microscope. Mean vertical discrepancy ranged from 22.6 to 62.2 microm, while horizontal discrepancy ranged from -27.1 to 16.0 microm. The microgap values of all I-A interfaces assessed in this study ranged from 2.3 to 5.6 microm. In conclusion, SEM images of I-A interface suggested no relationship between the geometrical factors and the type of anti-rotation configuration.
92 citations
TL;DR: Experimental data showed that the CQ-amine system could be completely replaced by Lucirin TPO when dual-wavelength LED unit was used for photoactivation.
Abstract: Despite good clinical acceptance, photoinitiating systems based on camphorquinone and amines raise concerns in terms of yellowing, aging, toxicity, or degradation in low pH conditions. This study aimed to prove whether CQ could be successfully replaced by alternative initiators in adhesive systems. Further, the efficiency of a prototype dual-wavelength LED (= Light Emitting Diode) curing unit was analyzed. In two commercial adhesive systems, CQ was completely replaced by Lucirin TPO. The commercial adhesives and their experimental counterparts were evaluated after curing for 10 seconds and 20 seconds with two dual-wavelength LED units and one regular LED unit, by applying the curing unit on the adhesive surface at two distances of 0 mm and 5 mm. Degree of cure and mechanical properties (Vickers hardness and modulus of elasticity) were assessed after 24-hour storage in distilled water at 37 degrees C. Experimental data showed that the CQ-amine system could be completely replaced by Lucirin TPO when dual-wavelength LED unit was used for photoactivation.
90 citations
TL;DR: On the effects of different surface conditioning methods, chairside and laboratory tribochemical silica coating followed by silanization showed higher bond strength results compared to those of aluminum oxide abrasion andsilanization, independent of the test method employed.
Abstract: This study tested the bond strength of a resin cement to a glass-infiltrated zirconia-alumina ceramic after three conditioning methods and using two test methods (shear-SBS versus microtensile-MTBS). Ceramic blocks for MTBS and ceramic disks for SBS were fabricated. Three surface conditioning (SC) methods were evaluated: (1) 110-mu m Al(2)O(3)+Silanization; (2) Chairside silica coating+silanization: (3) Laboratory silica coating+silanization. Following surface conditioning, the resin cement (Panavia F) was bonded to the conditioned ceramics. Although no statistically significant differences (p=0.1076) were seen between the test methods, results yielded with the different surface conditioning methods showed statistically significant differences (pSC1.). As for the interaction between the factors, two-way ANOVA showed that it was not statistically significant (p=0.1443). MTBS test resulted in predominantly mixed failure (85%), but SBS test resulted in exclusively adhesive failure. On the effects of different surface conditioning methods, chairside and laboratory tribochemical silica coating followed by silanization showed higher bond strength results compared to those of aluminum oxide abrasion and silanization, independent of the test method employed.
86 citations
TL;DR: Stability occurred within 2 weeks for all the eight materials when in water, while GC Fuji Plus, Maxcem, Panavia F and seT took 3 to 4 weeks to stabilize in ethanol:water.
Abstract: This study examined the solubility, sorption, and dimensional change of eight luting cements in two different solutions: 50% ethanol:water and distilled water. Ten disk specimens were prepared of each material following the manufacturers instructions, and then ground with silicone carbide paper. Sorption and solubility were calculated by weighing the specimens before and after immersion and desiccation. Data were analyzed by two-way ANOVA, Tukey's HSD and Fisher's PLSD tests. GC Fuji Plus and RelyX Luting2 showed the highest values of sorption and solubility both in water and ethanol:water. The percentage changes in volume for Maxcem, Nexus 2, Panavia F, RelyX Veneer, and VariolinkII were considerably smaller than for GC Fuji Plus, RelyX Luting2, and seT in both water and ethanol:water and after desiccation. Stability occurred within 2 weeks for all the eight materials when in water, while GC Fuji Plus, Maxcem, Panavia F and seT took 3 to 4 weeks to stabilize in ethanol:water.
86 citations
TL;DR: It was concluded that APO and BAPO photoinitiators exhibited reactivity comparable to that of CQ/tertiary amine system.
Abstract: The aims of this study were to investigate the photoinitiation behaviors of acylphosphine oxide (APO) and bisacylphosphine oxide (BAPO) derivatives in comparison to D,L-camphorquinone (CQ)/tertiary amine (EDAB) system. Fifty six kinds of experimental unfilled, light-cured resins were prepared using APO, BAPO, CQ, EDAB, resin monomers, and adhesive monomers. The measurements of ultraviolet-visible (UV-VIS) spectroscopy, photopolymerization with differential scanning calorimeter (photo-DSC) and degree of conversion (DC) determination were performed. Results showed that the UV-VIS spectra of all APO and BAPO derivatives possessed lambda max ranging between 365 and 416 nm. Their photoinitiation behaviors were not influenced by acidic adhesive monomers formulated in unfilled Bis-GMA-based resins (p < 0.05). Although BAPO exhibited higher reactivity than CQ/EDAB in unfilled 6-methacryloyloxyhexcyl phosphonoacetate (6-MHPA)/ 2-hydroxyethyl methacrylate (HEMA) and 6-MHPA/glycerol monomethacrylate (GM)-based resins, it was found that there were no statistically significant differences in DC (%) between BAPO [44.2(6.5)-51.2(4.3)] and CQ/EDAB [42.4(4.4)-47.5(3.7)] (p < 0.05). It was concluded that APO and BAPO photoinitiators exhibited reactivity comparable to that of CQ/tertiary amine system.
TL;DR: Results suggested that replacement of such composite restorations may be required after bleaching, as the effects of three bleaching agents on the color change and refractive index of three dental composites.
Abstract: This study investigated the effects of three bleaching agents (Whiteness Perfect, Whiteness Super, and Whiteness HP) on the color change and refractive index of three dental composites (Admira, Durafill VS, and Gradia Direct). Twenty disk-shaped specimens (10 x 2 mm) of each composite were prepared and divided into four subgroups (n=5). An unbleached group was used as a control, while the remaining specimens in the three subgroups were bleached with one of the bleaching agents respectively. Color change was assessed according to CIELAB color system and refractive indices were determined by phase modulated spectroscopic ellipsometry. Color differences between bleaching and baseline value (DeltaE) were less than 3.3 for all groups. However, bleaching with Whiteness HP led to noticeable color changes for Admira and Durafill VS. While this agent had no effect on the refractive indices of these composites, the other two agents containing carbamide peroxide increased their refractive indices. Therefore, results suggested that replacement of such composite restorations may be required after bleaching.
TL;DR: A novel, injectable bone tissue engineering material was developed that consisted of beta-tricalcium phosphate beads as the solid phase and alginate as the gel phase and showed support for osteogenic differentiation.
Abstract: A novel, injectable bone tissue engineering material was developed that consisted of β-tricalcium phosphate (β-TCP) beads as the solid phase and alginate as the gel phase. To prepare the instantaneously formed composite scaffold, an aqueous calcium chloride solution was dried on the surface of β-TCP beads and crosslinked with an alginic acid sodium solution, thereby forming stable β-TCP beads and alginate gel which were injectable via a syringe. This biodegradable composite was a three-dimensional (3D) material that could be used as an injectable scaffold for bone tissue engineering. In particular, the composite with 2.0 wt% alginate concentration exhibited a compressive strength of 69 kPa in dry conditions, which was significantly higher than that exhibited by 1.0 wt%. Furthermore, mesenchymal stem cells (MSC) were 3D-cultured within the composite and then investigated for osteogenic markers. MSC-loaded composite was subjected to scanning electron microscope (SEM) examination and implanted subcutaneously for in vivo experiment. Results showed that the scaffold provided support for osteogenic differentiation. In light of the encouraging results obtained, this novel injectable composite material may be useful for bone tissue engineering.
TL;DR: Based on the results of this in vitro study, a shoulder preparation is highly recommended whenever possible for endodontically treated teeth that are structurally compromised or which have anatomically limited areas, the slight chamfer preparation is an optimal recommendation.
Abstract: The aim of this in vitro study was to evaluate the effects of different preparation designs on the fracture resistance of single-crown zirconia frameworks. To this end, maxillary molar dies of CrCo alloy were fabricated with five different preparation designs: shoulderless, slight and pronounced deep chamfer, beveled and non-beveled shoulder. Ten zirconia copings with a wall thickness of 0.4 mm were fabricated for each type of preparation. After cementation by glass ionomer cement, they were loaded until fracture. There were significant differences in the breaking load of the experimental groups (ANOVA, p<0.01). The shoulder preparation had a mean breaking load of 2286 N, the shoulderless preparation 2041 N, the beveled shoulder 1722 N, the pronounced deep chamfer 1752 N, and the slight chamfer 1624 N. Based on the results of this study, a shoulder preparation is highly recommended whenever possible. Moreover, for endodontically treated teeth that are structurally compromised or which have anatomically limited areas, the slight chamfer preparation is an optimal recommendation.
TL;DR: A preparation angle of 12 degrees is recommended with the confidence that the marginal gap will be consistently less than 50 microm, and no statistically significant influences were detected between copings prepared using the laboratory and milling-center CAD/CAM systems.
Abstract: The aim of this in vitro study was to evaluate the effects of different preparation angles on the precision of fit of zirconia crown frameworks. Dies were fabricated with three different preparation angles: 4, 8, and 12 degrees total taper. Ten copings were fabricated for each angle by a laboratory and a milling-center CAD/CAM system. After cementation, cross-sections were obtained and cement gaps were measured. Preparation angle (ANOVA, p < 0.01) and measurement location (ANOVA, p < 0.01) exhibited statistically significant influence on the precision of fit. On the other hand, no statistically significant influences were detected between copings prepared using the laboratory and milling-center CAD/CAM systems (ANOVA, p = 0.92). All groups showed marginal openings ranging between 36.6 and 45.5 microm. In light of the results obtained in this study, a preparation angle of 12 degrees is hence recommended with the confidence that the marginal gap will be consistently less than 50 microm.
TL;DR: SEM observation of the polished surfaces showed that wrought CP Ti was even and completely featureless, while wrought Ti-6Al-4V alloy was pitted, and a needle-like phase containing traces of iron was observed on the polished surface.
Abstract: A newly developed electropolishing system, equipped with an original agitation function for an electrolyte and using a safe electrolyte composed of an alcoholic solution, was applied for wrought and cast CP titanium and its alloys. Surface roughness and morphology of the polished surfaces were then examined. Under an electrolytic condition of 70-75 V, 2.0 kA/m2, and 30 degrees C, wrought CP Ti and Ti-6Al-4V alloy achieved an apparent mirror-like finishing with an average surface roughness (Ra) of 0.03 and 0.12 microm respectively. Under the same condition, on the other hand, cast CP Ti and Ti-6Al-7Nb alloy produced rougher polished surfaces with average Ra values of 0.67-0.80 microm, and the finishing was apparently shiny, but not mirror-like. SEM observation of the polished surfaces showed that wrought CP Ti was even and completely featureless, while wrought Ti-6Al-4V alloy was pitted. For cast CP Ti, a needle-like phase containing traces of iron was observed on the polished surface.
TL;DR: It was concluded that the coating materials incorporated with FAAO possessed self-cleaning properties and displayed signs of inhibiting biofilm formation on their surfaces.
Abstract: The purpose of this study was to evaluate the inhibition of biofilm formation on newly developed coating materials with self-cleaning properties. A series of experimental coating materials containing fluoroalkylated acrylic acid oligomer (FAAO) were applied to resin composite substrates. The surfaces of the coating materials were analyzed by X-ray photoelectron spectroscopy (XPS) and contact angle measurement. Biofilm formation on the surface was assessed using Streptococcus mutans biofilms inside an oral simulator in vitro. The results indicated that an increase in the concentration of FAAO in the coating materials enhanced surface hydrophilicity and oil-repellency. Biofilm assays demonstrated that the amount of biofilm retained on the coating materials gradually decreased when the concentration of FAAO increased in the materials. It was concluded that the coating materials incorporated with FAAO possessed self-cleaning properties and displayed signs of inhibiting biofilm formation on their surfaces.
TL;DR: It was concluded that etching with concentrated sulfuric acid was a simple and effective way to roughen the surface of titanium without compromising its biocompatibility.
Abstract: The purpose of this study was to evaluate the effects of acid-etched titanium on the biological responses of osteoblast-like MC3T3-E1 cells. Four types of treatments (polishing, sandblasting, concentrated H2SO4 etching, and concentrated H2SO4 etching with vacuum firing) were carried out on the surfaces of commercially pure titanium (cpTi) disks. MC3T3-E1 cells were then cultured on the treated cpTi surfaces. Through surface roughness measurement and SEM analysis, it was found that the acid-etched surfaces showed higher roughness values than the sandblasted ones. Scanning electron microscope analysis showed that the cells on the disks treated with acid-etching and acid-etching with vacuum firing spread as well as the sandblasted ones. There were no significant differences in cell proliferation and collagen production on cpTi among the four different surface treatments. Based on the results of this study, it was concluded that etching with concentrated sulfuric acid was a simple and effective way to roughen the surface of titanium without compromising its biocompatibility.
TL;DR: It is suggested that to reduce stress in the remaining radicular tooth with a large coronal defect, it is recommended to accompany a composite resin core with a fiber post of a large diameter.
Abstract: Using three-dimensional finite element analysis (3D-FEA), stress distributions in the remaining radicular tooth structure were investigated under the condition of varying diameters of fiber post for fiber post-reinforced composite resin cores (fiber post and core) in maxillary central incisors. Four 3D-FEA models were constructed: (1) fiber post (φ1.2, φ1.4, and φ1.6 mm) and composite resin core; and (2) gold-cast post and core. Maximum stresses in the tooth structure for fiber post and core were higher than that for gold-cast post and core. In the former models, stresses in the tooth structure as well as in the composite resin were slightly reduced with increase in fiber post diameter. These results thus suggested that to reduce stress in the remaining radicular tooth with a large coronal defect, it is recommended to accompany a composite resin core with a fiber post of a large diameter.
TL;DR: Decomposition of the matrix resin and fallout of the fillers were observed in flowable resins that eroded with acidic and alcoholic drinks and it was thought that the lower the filler percentage, the greater was the surface degradation.
Abstract: The purpose of this study was to evaluate the morphological changes of the surfaces of flowable resins eroded by orange juice and alcohol drinks. The tested products were Beautifil Flow BF02 and BF10, Clearfil Majesty LV, FiltekTM Supreme XT Flowable Restorative, Unifil LoFlo Plus and FiltekTM Supreme. Filler percentages of flowable resins were calculated after the latter were incinerated at 750°C. Specimens were shaped into a disk form with a diameter of 10 mm and a thickness of 1 mm. Morphological changes were evaluated for the following types of flowable resin surfaces: polished surface, surfaces eroded by 100% orange juice, wine and whisky. Filler percentages of the tested flowable resins ranged between 42 and 78%. Surface degradation was observed for the specimens immersed in acidic and alcoholic drinks, and it was thought that the lower the filler percentage, the greater was the surface degradation. Decomposition of the matrix resin and fallout of the fillers were observed in flowable resins that eroded with acidic and alcoholic drinks.
TL;DR: Investigation of the characteristics of output light from different types of light curing units, and their effects on polymerization of light-activated composite resin indicated that markedly inhomogeneous light emitted from light curing unit could result in inhomogeneity polymerization in some areas of the restoration below the light guide tip.
Abstract: This study investigated the characteristics of output light from different types of light curing units, and their effects on polymerization of light-activated composite resin. Three quartz-tungsten-halogen lamps, one plasma arc lamp, and one LED light curing unit were used. Intensity distribution of light emitted from the light guide tip was measured at 1.0-mm intervals across the guide tip. Distribution of Knoop hardness number on the surface of resin irradiated with the light curing units was also measured. For all units, inhomogeneous distribution of light intensity across the guide tip was observed. Minimum light intensity values were 19-80% of the maximum values. In terms of surface hardness, inhomogeneous distribution was also observed for the materials irradiated with the tested units. Minimum values were 53-92% of the maximum values. Our results indicated that markedly inhomogeneous light emitted from light curing unit could result in inhomogeneous polymerization in some areas of the restoration below the light guide tip.
TL;DR: Structural and phase analyses showed that hydroxyapatite coatings produced by dynamic voltage during electrophoretic deposition (EPD) were free of cracks and decomposition of HA coatings was not observed until 800 degrees C.
Abstract: The aim of this study was to evaluate hydroxyapatite (HA) coatings produced by dynamic voltage during electrophoretic deposition (EPD). Dynamic voltages from 0 to 200 V were incrementally applied in three interims. The as-deposited coating was sintered at 800°C and its properties evaluated. Structure and phase analyses of both as-deposited and sintered coatings were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The HA coatings obtained by dynamic voltage consisted of two layers. While the inner layer was dense and firmly attached to the substrate and contained fine HA particles, the outer layer was porous and contained bigger particles. Repeated deposition was applied to increase the thickness of the coatings. SEM analysis showed that these coatings were free of cracks. In addition, decomposition of HA coatings was not observed until 800°C.
TL;DR: Mechanical and thermal cycling decreased the mean flexural strength values significantly for all the three ceramic-cpTi combinations tested when compared to the control group.
Abstract: This study evaluated the effects of mechanical and thermal cycling on the flexural strength (ISO 9693) of three brands of ceramics fused to commercially pure titanium (cpTi). Metallic frameworks of 25 x 3 x 0.5 mm dimensions (N= 84) were cast in cpTi, followed by 150- microm aluminum oxide airborne particle abrasion at a designated area of the frameworks (8 x 3 mm). Bonder and opaque ceramic were applied on the frameworks, and then the corresponding ceramic (Triceram, Super Porcelain Ti-22, Vita Titankeramik) was fired onto them (thickness: 1 mm). Half of the specimens from each ceramic-metal combination were randomly tested without aging (only water storage at 37 degrees C for 24 hours), while the other half were mechanically loaded (20,000 cycles under 10 N load, immersion in distilled water at 37 degrees C) and thermocycled (3,000 cycles, between 5-55 degrees C, dwell time of 13 seconds). After the flexural strength test, failure types were noted. Mechanical and thermal cycling decreased the mean flexural strength values significantly (p<0.05) for all the three ceramic-cpTi combinations tested when compared to the control group. In all the three groups, failure type was exclusively adhesive at the opaque ceramic-cpTi interfacial zone with no presence of ceramic on the substrate surface except for a visible oxide layer.
TL;DR: Results showed that Rocatec treatment was an effective way to prevent marginal leakage and shear bond strength value was found for RelyX and # 600 polishing combination.
Abstract: To evaluate the interactive influence of adhesive materials and surface treatments on bond strength of zirconium oxide ceramics, six types of adhesive resin cements (RelyX ARC (RA), Super-Bond C & B (SB), Linkmax (LM), Panavia Fluoro Cement (PF), Bistite II (BT), and Imperva Dual (ID)), three types of resin-reinforced glass ionomer cements (Xeno Cem Plus (XC), Vitremer Luting (VR), and Fuji Luting (FL)), as well as four types of surface treatments (# 600 polishing, sandblasting, silane, and Rocatec system) were used in this study. Results of this study indicated that all the tested adhesive materials treated with Rocatec system achieved the highest shear bond strength (31.9-67.1 MPa). In particular, the highest shear bond strength value of 67.1 MPa was found for Linkmax and Rocatec treatment combination, while the lowest shear bond strength value of 5.4 MPa was found for RelyX and # 600 polishing combination. Furthermore, results showed that Rocatec treatment was an effective way to prevent marginal leakage.
TL;DR: With unsilanized filler, the delta E value of composite resin artificial teeth was significantly increased, and the influences of filler type and discoloration medium, and their interaction thereof, were significant.
Abstract: In this study, the effects of filler type and polishing on the discoloration of composite resin artificial teeth were examined Four types of experimental resins were prepared: one was a matrix resin, while the others were composite resins containing three different types of fillers (nano-sized silica filler with or without silanization, and prepolymerized filler) Specimens were immersed in distilled water, coffee, red wine, or curry Color change after immersion was measured using a colorimeter Color difference values (delta E) and changes in translucency parameter (delta TP) were statistically analyzed using three-way ANOVA and Tukey's comparison On the influence of the polishing factor, statistically significant differences were neither observed in delta E nor delta TP between polished and non-polished tooth surfaces On the contrary, the influences of filler type and discoloration medium, and their interaction thereof, were significant With unsilanized filler, the delta E value of composite resin artificial teeth was significantly increased
TL;DR: Given the results obtained, GFP1 was the most suitable material for post fabrication since this model showed a lower stress value, which would therefore mean a lower possibility of root fracture.
Abstract: Although composite resin core is used with various types of prefabricated posts, it remains unclear which kind of material is most suitable for the post. The aim of this study was to evaluate the influence of prefabricated posts on the stress distribution within the root by finite element analysis. Posts and cores were built up with composite resin and four types of prefabricated posts: two types of glass fiber posts (GFP1, GFP2) with low and high Young's moduli, a titanium post (TIP), and a stainless steel post (SSP). In all models, stress distribution during function was calculated. There were differences in stress concentration at the root around the end of posts. The magnitudes of stress for GFP1, GFP2, TIP, and STP were 8.7, 9.3, 11.7, and 13.9 MPa respectively. Given the results obtained, GFP1 was the most suitable material for post fabrication since this model showed a lower stress value. It would therefore mean a lower possibility of root fracture.
TL;DR: In light of the surface roughness results obtained, one-step polishing systems seemed to be a good choice for polishing flowable composites.
Abstract: The purpose of this study was to investigate the influence of one-step polishing systems on the surface roughness of different flowable composites and a microhybrid composite. A total of 120 disks were fabricated and divided into six groups according to the different composite restorative materials tested (n=20). Each group was further divided into four subgroups according to the polishing system (n=5). For the control group, samples were left undisturbed after removal of Mylar strip. For the other three subgroups, samples were polished with PoGo, OptraPol, or Sof-Lex disks. Surface roughness was determined using a profilometer and observed under scanning electron microscope (SEM). Data were analyzed by one-way ANOVA and Duncan′s multiple range test. For Tetric Flow, Grandio Flow, Filtek Supreme XT Flow, and Admira Flow, their lowest surface roughness values were obtained in Mylar Strip and PoGo groups. For Compoglass Flow, there were no significant differences between Mylar Strip, PoGo, and OptraPol. For Filtek Z250, the lowest surface roughness value was obtained with Mylar Strip. In light of the surface roughness results obtained, one-step polishing systems seemed to be a good choice for polishing flowable composites.
TL;DR: Results showed that bond strength and nanoleakage formation depended on the bonding substrate (wet versus dry dentin) before bonding, and one-bottle self-etching adhesives might suck the water from dentinal tubules during bonding by osmosis, leading to nanoleAKage formation and thus a decline in bond strength.
Abstract: This study evaluated the effect of water on dentin substrate bonding of one-bottle self-etching adhesives. Dentin substrates were divided into two groups: wet and dry dentin. Wet dentin is the normal substrate for bond testing whereas dry dentin was dehydrated in a desiccator for 24 hours. Bonded dehydrated teeth were then divided into two subgroups: stored in water or in desiccator for 24 hours. Microtensile bond strength of resin to dentin was measured using three one-bottle self-etching adhesives. In addition, nanoleakage evaluation was performed through the analyses of SEM and TEM micrographs. The bond strength of dry-dentin group was significantly greater than that of wet-dentin. Further, the amount of nanoleakage within the adhesive interface of dry-dentin group was less than that of wet-dentin. Results showed that bond strength and nanoleakage formation depended on the bonding substrate (wet versus dry dentin) before bonding. One-bottle self-etching adhesives might suck the water from dentinal tubules during bonding by osmosis, leading to nanoleakage formation and thus a decline in bond strength.
TL;DR: Results of this study showed that both self-etching systems seemed to offer more merits than conventional acid etching because of fewer irreversible changes to enamel.
Abstract: This study sought to assess the efficacy of two self-etching primer systems (Transbond Plus and Beauty Ortho Bond) on orthodontic brackets. Therefore, shear bond strengths and bracket-adhesive failure modes (ARI scores) were determined and compared against an etch-and-rinse adhesive system (Transbond XT) under two experimental conditions (dry and saliva application). Shear bond strength test was performed at a crosshead speed of 0.5 mm/min, while enamel surfaces and enamel-adhesive interfaces were examined with SEM. There were no significant differences between Transbond XT (9.15 MPa) and Transbond Plus (9.74 MPa) under the dry condition, whereas that of Beauty Ortho Bond (6.47 MPa) was significantly lower than these two systems. Under SEM examination, both self-etching primers showed a milder etching effect and decreased depth of resin penetration into intact enamel than Transbond XT. In conclusion, results of this study showed that both self-etching systems seemed to offer more merits than conventional acid etching because of fewer irreversible changes to enamel.
TL;DR: The clinical performance of all soft liners was slightly impaired over the 12-month observation and except for cases showing extensive fungal colonization, the observed changes in clinical performance did not necessitate remaking of the dentures.
Abstract: Objective: The aim of the present study was to evaluate the clinical performance of four denture soft liners up to 12 months. Materials and methods: Thirty-three edentulous patients who experienced difficulties when using hard denture bases because of changes in denture-supporting tissues were accepted for the study and randomly received Molloplast B, GC Reline Soft, Silagum Comfort, or Mollosil Plus relines. Performance of the materials was evaluated using nine criteria at 3, 6, and 12 months: physical integrity, surface detail, adhesion, color, odor, plaque accumulation, resilience, hygiene, and mucosal condition. A four-point categorized scale (1=poor, 2=fair, 3=good, 4=excellent) was used. Unscheduled maintenance events and the presence of fungal colonization were also recorded. Results: The percentage of patients available at 3, 6, and 12 months were 91%, 91%, and 66%. Main reasons for dropouts and discontinuation were fractured dentures and patient dissatisfaction. At 6 months, 96% of the performance scores were good or excellent and the largest changes were observed for physical integrity, surface detail, color, and fungal colonization. Fungal colonization was the most commonly observed problem and was the only reason of failure at 12 months. Conclusions: The clinical performance of all soft liners was slightly impaired over the 12-month observation. Except for cases showing extensive fungal colonization, the observed changes in clinical performance did not necessitate remaking of the dentures. Mollosil Plus showed a performance comparable to that of Molloplast B, and the other materials had slightly lower performance especially in terms of fungal colonization.